1. Field of the Invention
The present invention relates to a double-sided meshing type silent chain capable of being engaged with sprockets on both inner and outer peripheral sides of the chain.
2. Description of the Related Art
As a conventional double-sided meshing type silent chain capable of meshing with sprockets on both the inner peripheral side (hereinafter "front side") and the outer peripheral side (hereinafter "rear side") of the chain through a large number of plates connected together in an endless manner, there is known, for example, such a silent chain as shown in FIG. 8. This silent chain 13 is assembled by connecting plates 11 and 12 in an endless fashion. It has teeth for engagement with a sprocket 14 located on an inner or outer peripheral side of the chain 13 and also has teeth for engagement with a sprocket 15 located on the opposite side. The plates 11 and 12 are centrally constricted and a pair of chevron-shaped teeth are formed on both sides of each plate.
FIG. 9 shows another example of a conventional both-side meshing type silent chain. This silent chain 24 is assembled in an endless manner. More particularly, plates 21 each having a pair of chevron-shaped teeth on the front side and being flat on the rear side and plates 22 each being flat on the front side and having a pair of chevron-shaped teeth on the rear side are alternately connected together with pins 23 to constitute the chain 24. There are disposed a sprocket 25 meshing with one of inner and outer periphery sides of the silent chain 24 and a sprocket 26 meshing with the other side. The sprockets 25 and 26 are each formed with teeth at two-pitch intervals, with which the teeth of the plates 21 and 22 come into engagement.
If any of the above conventional silent chains capable of meshing with sprockets on both inner and outer peripheral sides of the chain is used as a timing chain for an automobile engine for example, it becomes possible to bring a sprocket into engagement with the outer periphery on a tension side of a chain circulation path and thereby draw the tension-side path as close as possible to a return-side path of the chain, whereby the space occupied by the entire chain circulation path can be diminished. However, since chevron-shaped teeth for engagement with sprocket teeth are formed on the rear side of the plate, it is difficult to bring the shoe faces of a tensioner and a chain guide into sliding contact with the rear face of the plate.
More particularly, if chevron-shaped teeth are formed on the rear side of the plate, the tops of the plate teeth come into contact with the shoe faces intermittently, so that the shoe faces are substantially worn out, leading to a shortening of their service life, or the vibration-preventing effect is decreased by the intermittent contact, thus causing wear elongation of the chain and leading to generation of noise.
In such a double-sided meshing type silent chain as shown in FIG. 9, which shows the chain coming into mesh with sprocket teeth at two-pitch intervals, the amplitude of a polygonal motion upon such engagement of the two is great and it becomes impossible to perform a smooth high-speed transmission of power. The problem of early-stage sprocket wear also results.